Hi! Welcome to the forums. For the workshop there is quite alot of items that require dlcs however each item tells you what dlc it needs, alot the older content has made made without dlc so great for new players
So for the workshop, find an item you would like to download and press the subscribe button, if you have the correct dlc (or none) the item will appear in the blueprints menu ingame. The blueprints menu has a middle section which is downloaded blueprints which are ready for placement.
If you do not have alot or any of the dlc , filter the search by most subscribed (should be a scroll menu in the center of the results). The most subscribed items are very popular items and many do not require any dlc to enjoy